Preamble and payload for high efficiency (he) transmission

ABSTRACT

In wireless communications, an access point may send a trigger frame to multiple stations. The trigger frame&#39;s payload may include a first content and a second content, where the first content is associated with a legacy signal field of an uplink frame, and the second content is associated with a non-legacy signal field of the uplink frame. In response to the trigger frame, one or more stations may generate the uplink frame(s) based on the trigger frame and transmit the uplink frame(s) to the access point. The uplink frame(s) may include a legacy signal field and a non-legacy signal field. The legacy field may include a length of the uplink frame(s) that is based on the first content. The non-legacy signal field may include a remaining transmission opportunity (TXOP) duration that is generated based on the second content. Other methods, apparatus, and computer-readable media are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalApplication No. 62/152,509, entitled “PREAMBLE FOR UL MU TRANSMISSION INHE WLAN,” filed Apr. 24, 2015, which is incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present description relates in general to wireless communicationsystems and methods, and more particularly to, for example, withoutlimitation, preamble and payload for high efficiency (HE) transmission.

BACKGROUND

Wireless local area network (WLAN) devices are deployed in diverseenvironments. These environments are generally characterized by theexistence of access points and non-access point stations. Increasedinterference from neighboring devices gives rise to performancedegradation. Additionally, WLAN devices are increasingly required tosupport a variety of applications such as video, cloud access, andoffloading. In particular, video traffic is expected to be the dominanttype of traffic in many high efficiency WLAN deployments. With thereal-time requirements of some of these applications, WLAN users demandimproved performance in delivering their applications, includingimproved power consumption for battery-operated devices.

The description provided in the background section should not be assumedto be prior art merely because it is mentioned in or associated with thebackground section. The background section may include information thatdescribes one or more aspects of the subject technology.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processor in a wireless communication device.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processor in a wireless communication device.

FIG. 4 illustrates an example of a timing diagram of interframe space(IFS) relationships.

FIG. 5 illustrates an example of a timing diagram of a carrier sensemultiple access/collision avoidance (CSMA/CA) based frame transmissionprocedure for avoiding collision between frames in a channel.

FIG. 6 illustrates an example of a high efficiency (HE) frame.

FIGS. 7, 8, and 9 illustrate schematic diagrams of examples of anexchange of frames among wireless communication devices forcommunication in a wireless network for multi-user (MU) transmission.

FIG. 10 illustrates an example of utilization of a duration in uplinkmulti-user physical layer convergence procedure (PLCP) protocol dataunit (PPDU) transmissions.

FIG. 11 illustrates an example of legacy signal (L-SIG) field and asignal-A (SIG-A) field transmission in UL MU PPDU.

FIG. 12 illustrates an example of an absolute frequency allocationinformation included in a SIG-A field of a UL MU PPDU.

FIG. 13 illustrates an example of a SIG field format for a 1 MHz nulldata packet (NDP) compressed media access control (CMAC) frame.

FIG. 14 illustrates an example of a SIG field format for a greater thanor equal to 2 MHz NDP CMAC frame.

FIG. 15 illustrates an example of an NDP clear to send (CTS) frame.

FIG. 16 illustrates an example of an NDP contention-free end (CF-End)frame.

FIG. 17 illustrates an example of an NDP power save-poll (PS-Poll)frame.

FIG. 18 illustrates an example of an NDP acknowledgement (Ack) frame.

FIG. 19 illustrates an example of an NDP power save-poll acknowledgement(PS-Poll-Ack) frame.

FIG. 20 illustrates an example of an NDP block acknowledgement(BlockAck) frame.

FIG. 21 illustrates an example of an NDP Beamforming Report Poll frame.

FIG. 22 illustrates an example of an NDP Paging frame.

FIG. 23 illustrates an example of an NDP Probe Request frame.

FIGS. 24A, 24B, and 24C illustrate flow charts of examples of methodsfor facilitating wireless communication for multi-user transmission.

In one or more implementations, not all of the depicted components ineach figure may be required, and one or more implementations may includeadditional components not shown in a figure. Variations in thearrangement and type of the components may be made without departingfrom the scope of the subject disclosure. Additional components,different components, or fewer components may be utilized within thescope of the subject disclosure.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious implementations and is not intended to represent the onlyimplementations in which the subject technology may be practiced. Asthose skilled in the art would realize, the described implementationsmay be modified in various different ways, all without departing fromthe scope of the present disclosure. Accordingly, the drawings anddescription are to be regarded as illustrative in nature and notrestrictive.

Multi-user (MU) transmission in next-generation WLAN systems includetechniques such as downlink/uplink (DL/UL) MUmultiple-input/multiple-output (MIMO) and DL/UL orthogonal frequencydivision multiple access (OFDMA). In the Institute of Electrical andElectronics Engineers (IEEE) 802.11, Task Group ax, (IEEE 802.11ax),OFDMA technology may be utilized to provide a multiple access scheme toimprove network efficiency. OFDMA is a technology that allows multiplestations (STAs) to transmit frames simultaneously using non-overlappingfrequency-time resources. IEEE 802.11ax may be referred to as HighEfficiency LAN (HE LAN) or High Efficiency WLAN (HE WLAN).

A trigger frame may be a frame sent by an AP that seeks data, control,or management frame response(s) from stations that participate in asubsequent UL MU frame. The trigger frame may be utilized to initiatethe MU simultaneous transmission in OFDMA. In an aspect, a trigger framemay include, for example, some or all of the following features: (a) alist of stations (STAs) that an access point (AP) seeks a response from;(b) resource allocation information for each STA (e.g., a sub-bandassigned to each STA); and/or (c) attributes of the expected UL MUframe, such as the duration, bandwidth, etc., among other features. Inother words, the trigger frame may be used to allocate resource for ULMU transmission and to solicit an UL MU transmission from theparticipating stations in response to the trigger frame. The term“resource” may refer to, for example, bandwidth, time/duration that theSTAs expect to occupy a transmission medium, and/or possibly a number ofspatial streams that the STAs may use.

In one or more implementations. in IEEE 802.11ax, a UL MU physical layerconvergence procedure (PLCP) protocol data unit (PPDU) (e.g., MU-MIMO orOFDMA) is sent as a response (e.g., an immediate response) to a triggerframe sent by an AP. The UL MU PPDUs may be, for example, referred to astrigger-based UL MU PPDUs, trigger-based UL PPDUs, HE trigger-based ULMU PPDU response, or a variant/combination thereof (e.g., HEtrigger-based UL MU PPDUs). In some aspects, since UL MU transmissionmay be triggered by an AP, a signal-A (SIG-A) field in a UL MU PPDU canhave a format different from downlink PPDUs or uplink single-user (SU)PPDUs. One or more aspects of the present disclosure provide a newdesign for a SIG-A field in UL MU PPDUs. The SIG-A field may includemodifications and/or additions to the SIG-A field of the very highthroughput (VHT) WLAN utilized in the IEEE 802.11ac standard, which isincorporated herein in its entirety.

In one or more implementations, contents in a preamble (e.g., legacysignal (L-SIG) field and SIG-A field) in UL MU PPDU may follow one ormore of the following traits:

-   -   UL MU PPDUs can have a different SIG-A from non-UL MU PPDUs        -   An indication bit(s) should be located in the same bit            positions with that (those) of non-UL MU SIG-A    -   Duration and absolute occupied frequency information can be        included in UL MU SIG-A        -   Duration for time-protection        -   Bandwidth and absolute channel number of 20 MHz for            frequency-protection    -   Null data packet (NDP) clear to send (CTS) frame format without        4 bit reservation can be used for SIG-A field in UL MU PPDU.        In an aspect, a non-UL MU PPDU may include, for example, one or        more of the following: a UL SU PPDU, a DL SU PPDU, and a DL MU        PPDU. In an aspect, UL MU SIG-A may refer to a SIG-A field of a        UL MU PPDU. In an aspect, non-UL MU SIG-A may refer to a SIG-A        field of a non-UL MU PPDU. In an aspect, the indication bit(s)        may be utilized to differentiate between UL MU PPDUs and non-UL        MU PPDUs. For instance, the indication bit(s) may be utilized to        differentiate between UL MU PPDU and SU PPDU.

FIG. 1 illustrates a schematic diagram of an example of a wirelesscommunication network 100. In the wireless communication network 100,such as a wireless local area network (WLAN), a basic service set (BSS)includes a plurality of wireless communication devices (e.g., WLANdevices). In one aspect, a BSS refers to a set of STAs that cancommunicate in synchronization, rather than a concept indicating aparticular area. In the example, the wireless communication network 100includes wireless communication devices 111-115, which may be referredto as stations (STAs).

Each of the wireless communication devices 111-115 may include a mediaaccess control (MAC) layer and a physical (PHY) layer according to anIEEE 802.11 standard. In the example, at least one wirelesscommunication device (e.g., device 111) is an access point (AP). An APmay be referred to as an AP STA, an AP device, or a central station. Theother wireless communication devices (e.g., devices 112-115) may benon-AP STAs. Alternatively, all of the wireless communication devices111-115 may be non-AP STAs in an Ad-hoc networking environment.

An AP STA and a non-AP STA may be collectively called STAs. However, forsimplicity of description, in some aspects, only a non-AP STA may bereferred to as a STA. An AP may be, for example, a centralizedcontroller, a base station (BS), a node-B, a base transceiver system(BTS), a site controller, a network adapter, a network interface card(NIC), a router, or the like. A non-AP STA (e.g., a client deviceoperable by a user) may be, for example, a device with wirelesscommunication capability, a terminal, a wireless transmit/receive unit(WTRU), a user equipment (UE), a mobile station (MS), a mobile terminal,a mobile subscriber unit, a laptop, a non-mobile computing device (e.g.,a desktop computer with wireless communication capability) or the like.In one or more aspects, a non-AP STA may act as an AP (e.g., a wirelesshotspot).

In one aspect, an AP is a functional entity for providing access to adistribution system, by way of a wireless medium, for an associated STA.For example, an AP may provide access to the internet for one or moreSTAs that are wirelessly and communicatively connected to the AP. InFIG. 1, wireless communications between non-AP STAs are made by way ofan AP. However, when a direct link is established between non-AP STAs,the STAs can communicate directly with each other (without using an AP).

In one or more implementations, OFDMA-based 802.11 technologies areutilized, and for the sake of brevity, a STA refers to a non-AP highefficiency (HE) STA, and an AP refers to an HE AP. In one or moreaspects, a STA may act as an AP.

FIG. 2 illustrates a schematic diagram of an example of a wirelesscommunication device. The wireless communication device 200 includes abaseband processor 210, a radio frequency (RF) transceiver 220, anantenna unit 230, a memory 240, an input interface unit 250, an outputinterface unit 260, and a bus 270, or subsets and variations thereof.The wireless communication device 200 can be, or can be a part of, anyof the wireless communication devices 111-115.

In the example, the baseband processor 210 performs baseband signalprocessing, and includes a medium access control (MAC) processor 211 anda PHY processor 215. The memory 240 may store software (such as MACsoftware) including at least some functions of the MAC layer. The memorymay further store an operating system and applications.

In the illustration, the MAC processor 211 includes a MAC softwareprocessing unit 212 and a MAC hardware processing unit 213. The MACsoftware processing unit 212 executes the MAC software to implement somefunctions of the MAC layer, and the MAC hardware processing unit 213 mayimplement remaining functions of the MAC layer as hardware (MAChardware). However, the MAC processor 211 may vary in functionalitydepending on implementation. The PHY processor 215 includes atransmitting (TX) signal processing unit 280 and a receiving (RX) signalprocessing unit 290. The term TX may refer to transmitting, transmit,transmitted, transmitter or the like. The term RX may refer toreceiving, receive, received, receiver or the like.

The PHY processor 215 interfaces to the MAC processor 211 through, amongothers, transmit vector (TXVECTOR) and receive vector (RXVECTOR)parameters. In one or more aspects, the MAC processor 211 generates andprovides TXVECTOR parameters to the PHY processor 215 to supplyper-packet transmit parameters. In one or more aspects, the PHYprocessor 215 generates and provides RXVECTOR parameters to the MACprocessor 211 to inform the MAC processor 211 of the received packetparameters.

In some aspects, the wireless communication device 200 includes aread-only memory (ROM) (not shown) or registers (not shown) that storeinstructions that are needed by one or more of the MAC processor 211,the PHY processor 215 and/or other components of the wirelesscommunication device 200.

In one or more implementations, the wireless communication device 200includes a permanent storage device (not shown) configured as aread-and-write memory device. The permanent storage device may be anon-volatile memory unit that stores instructions even when the wirelesscommunication device 200 is off. The ROM, registers and the permanentstorage device may be part of the baseband processor 210 or be a part ofthe memory 240. Each of the ROM, the permanent storage device, and thememory 240 may be an example of a memory or a computer-readable medium.A memory may be one or more memories.

The memory 240 may be a read-and-write memory, a read-only memory, avolatile memory, a non-volatile memory, or a combination of some or allof the foregoing. The memory 240 may store instructions that one or moreof the MAC processor 211, the PHY processor 215, and/or anothercomponent may need at runtime.

The RF transceiver 220 includes an RF transmitter 221 and an RF receiver222. The input interface unit 250 receives information from a user, andthe output interface unit 260 outputs information to the user. Theantenna unit 230 includes one or more antennas. When multi-inputmulti-output (MIMO) or multi-user MIMO (MU-MIMO) is used, the antennaunit 230 may include more than one antenna.

The bus 270 collectively represents all system, peripheral, and chipsetbuses that communicatively connect the numerous internal components ofthe wireless communication device 200. In one or more implementations,the bus 270 communicatively connects the baseband processor 210 with thememory 240. From the memory 240, the baseband processor 210 may retrieveinstructions to execute and data to process in order to execute theprocesses of the subject disclosure. The baseband processor 210 can be asingle processor, multiple processors, or a multi-core processor indifferent implementations. The baseband processor 210, the memory 240,the input interface unit 250, and the output interface unit 260 maycommunicate with each other via the bus 270.

The bus 270 also connects to the input interface unit 250 and the outputinterface unit 260. The input interface unit 250 enables a user tocommunicate information and select commands to the wirelesscommunication device 200. Input devices that may be used with the inputinterface unit 250 may include any acoustic, speech, visual, touch,tactile and/or sensory input device, e.g., a keyboard, a pointingdevice, a microphone, or a touchscreen. The output interface unit 260may enable, for example, the display or output of videos, images, audio,and data generated by the wireless communication device 200. Outputdevices that may be used with the output interface unit 260 may includeany visual, auditory, tactile, and/or sensory output device, e.g.,printers and display devices or any other device for outputtinginformation. One or more implementations may include devices thatfunction as both input and output devices, such as a touchscreen.

One or more implementations can be realized in part or in whole using acomputer-readable medium. In one aspect, a computer-readable mediumincludes one or more media. In one or more aspects, a computer-readablemedium is a tangible computer-readable medium, a computer-readablestorage medium, a non-transitory computer-readable medium, amachine-readable medium, a memory, or some combination of the foregoing(e.g., a tangible computer-readable storage medium, or a non-transitorymachine-readable storage medium). In one aspect, a computer is amachine. In one aspect, a computer-implemented method is amachine-implemented method.

A computer-readable medium may include storage integrated into aprocessor and/or storage external to a processor. A computer-readablemedium may be a volatile, non-volatile, solid state, optical, magnetic,and/or other suitable storage device, e.g., RAM, ROM, PROM, EPROM, aflash, registers, a hard disk, a removable memory, or a remote storagedevice.

In one aspect, a computer-readable medium comprises instructions storedtherein. In one aspect, a computer-readable medium is encoded withinstructions. In one aspect, instructions are executable by one or moreprocessors (e.g., 210, 211, 212, 213, 215, 280, 290) to perform one ormore operations or a method. Instructions may include, for example,programs, routines, subroutines, data, data structures, objects,sequences, commands, operations, modules, applications, and/orfunctions. Those skilled in the art would recognize how to implement theinstructions.

A processor (e.g., 210, 211, 212, 213, 215, 280, 290) may be coupled toone or more memories (e.g., one or more external memories such as thememory 240, one or more memories internal to the processor, one or moreregisters internal or external to the processor, or one or more remotememories outside of the device 200), for example, via one or more wiredand/or wireless connections. The coupling may be direct or indirect. Inone aspect, a processor includes one or more processors. A processor,including a processing circuitry capable of executing instructions, mayread, write, or access a computer-readable medium. A processor may be,for example, an application specific integrated circuit (ASIC), adigital signal processor (DSP), or a field programmable gate array(FPGA).

In one aspect, a processor (e.g., 210, 211, 212, 213, 215, 280, 290) isconfigured to cause one or more operations of the subject disclosure tooccur. In one aspect, a processor is configured to cause an apparatus(e.g., a wireless communication device 200) to perform operations or amethod of the subject disclosure. In one or more implementations, aprocessor configuration involves having a processor coupled to one ormore memories. A memory may be internal or external to the processor.Instructions may be in a form of software, hardware or a combinationthereof. Software instructions (including data) may be stored in amemory. Hardware instructions may be part of the hardware circuitrycomponents of a processor. When the instructions are executed orprocessed by one or more processors, (e.g., 210, 211, 212, 213, 215,280, 290), the one or more processors cause one or more operations ofthe subject disclosure to occur or cause an apparatus (e.g., a wirelesscommunication device 200) to perform operations or a method of thesubject disclosure.

FIG. 3A illustrates a schematic block diagram of an example of atransmitting signal processing unit 280 in a wireless communicationdevice. The transmitting signal processing unit 280 of the PHY processor215 includes an encoder 281, an interleaver 282, a mapper 283, aninverse Fourier transformer (IFT) 284, and a guard interval (GI)inserter 285.

The encoder 281 encodes input data. For example, the encoder 281 may bea forward error correction (FEC) encoder. The FEC encoder may include abinary convolutional code (BCC) encoder followed by a puncturing device,or may include a low-density parity-check (LDPC) encoder. Theinterleaver 282 interleaves the bits of each stream output from theencoder 281 to change the order of bits. In one aspect, interleaving maybe applied only when BCC encoding is employed. The mapper 283 maps thesequence of bits output from the interleaver 282 into constellationpoints.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may use multiple instances of the interleaver 282 and multipleinstances of the mapper 283 corresponding to the number of spatialstreams (N_(SS)). In the example, the transmitting signal processingunit 280 may further include a stream parser for dividing outputs of theBCC encoders or the LDPC encoder into blocks that are sent to differentinterleavers 282 or mappers 283. The transmitting signal processing unit280 may further include a space-time block code (STBC) encoder forspreading the constellation points from the number of spatial streamsinto a number of space-time streams (N_(STS)) and a spatial mapper formapping the space-time streams to transmit chains. The spatial mappermay use direct mapping, spatial expansion, or beamforming depending onimplementation. When MU-MIMO is employed, one or more of the blocksbefore reaching the spatial mapper may be provided for each user.

The IFT 284 converts a block of the constellation points output from themapper 283 or the spatial mapper into a time domain block (e.g., asymbol) by using an inverse discrete Fourier transform (IDFT) or aninverse fast Fourier transform (IFFT). If the STBC encoder and thespatial mapper are employed, the IFT 284 may be provided for eachtransmit chain.

When MIMO or MU-MIMO is employed, the transmitting signal processingunit 280 may insert cyclic shift diversities (CSDs) to preventunintentional beamforming. The CSD insertion may occur before or afterthe inverse Fourier transform operation. The CSD may be specified pertransmit chain or may be specified per space-time stream. Alternatively,the CSD may be applied as a part of the spatial mapper.

The GI inserter 285 prepends a GI to the symbol. The transmitting signalprocessing unit 280 may optionally perform windowing to smooth edges ofeach symbol after inserting the GI. The RF transmitter 221 converts thesymbols into an RF signal and transmits the RF signal via the antennaunit 230. When MIMO or MU-MIMO is employed, the GI inserter 285 and theRF transmitter 221 may be provided for each transmit chain.

FIG. 3B illustrates a schematic block diagram of an example of areceiving signal processing unit 290 in a wireless communication device.The receiving signal processing unit 290 of the PHY processor 215includes a GI remover 291, a Fourier transformer (FT) 292, a demapper293, a deinterleaver 294, and a decoder 295.

The RF receiver 222 receives an RF signal via the antenna unit 230 andconverts the RF signal into one or more symbols. In some aspects, the GIremover 291 removes the GI from the symbol. When MIMO or MU-MIMO isemployed, the RF receiver 222 and the GI remover 291 may be provided foreach receive chain.

The FT 292 converts the symbol (e.g., the time domain block) into ablock of the constellation points by using a discrete Fourier transform(DFT) or a fast Fourier transform (FFT) depending on implementation. Inone or more implementations, the FT 292 is provided for each receivechain.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may further include a spatial demapper for converting the Fouriertransformed receiver chains to constellation points of the space-timestreams, and a STBC decoder (not shown) for despreading theconstellation points from the space-time streams into the spatialstreams.

The demapper 293 demaps the constellation points output from the FT 292or the STBC decoder to the bit streams. If the LDPC encoding is used,the demapper 293 may further perform LDPC tone demapping before theconstellation demapping. The deinterleaver 294 deinterleaves the bits ofeach stream output from the demapper 293. In one or moreimplementations, deinterleaving may be applied only when BCC decoding isused.

When MIMO or MU-MIMO is employed, the receiving signal processing unit290 may use multiple instances on the demapper 293 and multipleinstances of the deinterleaver 294 corresponding to the number ofspatial streams. In the example, the receiving signal processing unit290 may further include a stream deparser for combining the streamsoutput from the deinterleavers 294.

The decoder 295 decodes the streams output from the deinterleaver 294and/or the stream deparser. For example, the decoder 295 may be an FECdecoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

FIG. 4 illustrates an example of a timing diagram of interframe space(IFS) relationships. In this example, a data frame, a control frame, ora management frame can be exchanged between the wireless communicationdevices 111-115 and/or other WLAN devices.

Referring to the timing diagram 400, during the time interval 402,access is deferred while the medium (e.g., a wireless communicationchannel) is busy until a type of IFS duration has elapsed. At timeinterval 404, immediate access is granted when the medium is idle for aduration that is equal to or greater than a distributed coordinationfunction IFS (DIFS) 410 duration or arbitration IFS (AIFS) 414 duration.In turn, a next frame 406 may be transmitted after a type of IFSduration and a contention window 418 have passed. During the time 408,if a DIFS has elapsed since the medium has been idle, a designated slottime 420 is selected and one or more backoff slots 422 are decrementedas long as the medium is idle.

The data frame is used for transmission of data forwarded to a higherlayer. In one or more implementations, a WLAN device transmits the dataframe after performing backoff if DIFS 410 has elapsed from a time whenthe medium has been idle.

The management frame is used for exchanging management information thatis not forwarded to the higher layer. Subtype frames of the managementframe include a beacon frame, an association request/response frame, aprobe request/response frame, and an authentication request/responseframe.

The control frame is used for controlling access to the medium. Subtypeframes of the control frame include a request to send (RTS) frame, aclear to send (CTS) frame, and an ACK frame. In the case that thecontrol frame is not a response frame of the other frame (e.g., aprevious frame), the WLAN device transmits the control frame afterperforming backoff if the DIFS 410 has elapsed. In the case that thecontrol frame is the response frame of the other frame, the WLAN devicetransmits the control frame without performing backoff if a short IFS(SIFS) 412 has elapsed. The type and subtype of frame may be identifiedby a type field and a subtype field in a frame control field of theframe.

On the other hand, a Quality of Service (QoS) STA may transmit the frameafter performing backoff if AIFS 414 for access category (AC), e.g.,AIFS[AC], has elapsed. In this case, the data frame, the managementframe, or the control frame that is not the response frame may use theAIFS[AC].

In one or more implementations, a point coordination function (PCF)enabled AP STA transmits the frame after performing backoff if a PCF IFS(PIFS) 416 has elapsed. In this example, the PIFS 416 duration is lessthan the DIFS 410 but greater than the SIFS 412. In some aspects, thePIFS 416 is determined by incrementing the SIFS 412 duration by adesignated slot time 420.

FIG. 5 illustrates an example of a timing diagram of a carrier sensemultiple access/collision avoidance (CSMA/CA) based frame transmissionprocedure for avoiding collision between frames in a channel. In FIG. 5,any one of the wireless communication devices 111-115 in FIG. 1 can bedesignated as one of STA1, STA2 or STA3. In this example, the wirelesscommunication device 111 is designated as STA1, the wirelesscommunication device 112 is designated as STA2, and the wirelesscommunication device 113 is designated as STA3. While the timing of thewireless communication devices 114 and 115 is not shown in FIG. 5, thetiming of the devices 114 and 115 may be the same as that of STA2.

In this example, STA1 is a transmit WLAN device for transmitting data,STA2 is a receive WLAN device for receiving the data, and STA3 is a WLANdevice that may be located at an area where a frame transmitted from theSTA1 and/or a frame transmitted from the STA2 can be received by theSTA3.

The STA1 may determine whether the channel (or medium) is busy bycarrier sensing. The STA1 may determine the channel occupation based onan energy level on the channel or correlation of signals in the channel.In one or more implementations, the STA1 determines the channeloccupation by using a network allocation vector (NAV) timer.

When determining that the channel is not used by other devices duringthe DIFS 410 (e.g., the channel is idle), the STA1 may transmit an RTSframe 502 to the STA2 after performing backoff. Upon receiving the RTSframe 502, the STA2 may transmit a CTS frame 506 as a response of theCTS frame 506 after the SIFS 412.

When the STA3 receives the RTS frame 502, the STA3 may set a NAV timerfor a transmission duration representing the propagation delay ofsubsequently transmitted frames by using duration information involvedwith the transmission of the RTS frame 502 (e.g., NAV(RTS) 510). Forexample, the STA3 may set the transmission duration expressed as thesummation of a first instance of the SIFS 412, the CTS frame 506duration, a second instance of the SIFS 412, a data frame 504 duration,a third instance of the SIFS 412 and an ACK frame 508 duration.

Upon receiving a new frame (not shown) before the NAV timer expires, theSTA3 may update the NAV timer by using duration information included inthe new frame. The STA3 does not attempt to access the channel until theNAV timer expires.

When the STA1 receives the CTS frame 506 from the STA2, the STA1 maytransmit the data frame 504 to the STA2 after the SIFS 412 elapses froma time when the CTS frame 506 has been completely received. Uponsuccessfully receiving the data frame 504, the STA2 may transmit the ACKframe 508 after the SIFS 412 elapses as an acknowledgment of receivingthe data frame 504.

When the NAV timer expires, the STA3 may determine whether the channelis busy by the carrier sensing. Upon determining that the channel is notused by the other WLAN devices (e.g., STA1, STA2) during the DIFS 410after the NAV timer has expired, the STA3 may attempt the channel accessafter a contention window 418 has elapsed. In this example, thecontention window 418 may be based on a random backoff.

FIG. 6 illustrates an example of a high efficiency (HE) frame 600. TheHE frame 600 is a physical layer convergence procedure (PLCP) protocoldata unit (or PPDU) format. An HE frame may be referred to as an OFDMAframe, a PPDU, a PPDU format, an OFDMA PPDU, an MU PPDU, another similarterm, or vice versa. An HE frame may be simply referred to as a framefor convenience. In one or more implementations, an AP may transmit aframe for downlink (DL) using a frame format shown in this figure or avariation thereof (e.g., without any or some portions of an HE header).A STA may transmit a frame for uplink (UL) using a frame format shown inthis figure or a variation thereof (e.g., without any or some portionsof an HE header).

Referring to FIG. 6, the HE frame 600 contains a header and a datafield. The header includes a legacy header comprised of a legacy shorttraining field (L-STF), a legacy long training field (L-LTF), and alegacy signal (L-SIG) field. These legacy fields contain symbols basedon an early design of an IEEE 802.11 specification. The L-STF, L-LTF,and L-SIG fields may be 8 μs, 8 μs, and 4 μs, respectively. Presence ofthese symbols would make any new design compatible with the legacydesigns and products. The legacy header may be referred to as a legacypreamble. In one or more aspects, the term header may be referred to asa preamble.

In one or more implementations, the legacy STF, LTF, and SIG symbols aremodulated/carried with FFT size of 64 on a 20 MHz sub-channel and areduplicated every 20 MHz if the frame has a channel bandwidth wider than20 MHz (e.g., 40 MHz, 80 MHz, 160 MHz). Therefore, the legacy field(i.e., the STF, LTF, and SIG fields) occupies the entire channelbandwidth of the frame. The L-STF field may be utilized for packetdetection, automatic gain control (AGC), and coarse frequency-offset(FO) correction. In one aspect, the L-STF field does not utilizefrequency domain processing (e.g., FFT processing) but rather utilizestime domain processing. Thus, in one aspect, the L-STF field is notaffected by the channel dispersion. The L-LTF field may be utilized forchannel estimation, fine frequency-offset correction, and symbol timing.The L-SIG field includes one orthogonal frequency division multiplexing(OFDM) symbol. Thus, in one aspect, the term L-SIG field may be usedinterchangeably with L-SIG symbol. In one or more aspects, the L-SIGfield may contain information indicative of a data rate and a length(e.g., in bytes) associated with the HE frame 600, which may be utilizedby a receiver of the HE frame 600 to calculate a time duration of atransmission of the HE frame 600.

The header may also include an HE header comprised of an HE-SIG-A fieldand an HE-SIG-B field. The HE-SIG-A field may sometimes be referred tosimply as a SIG-A field. These fields contain symbols that carry controlinformation that may be vital regarding each PLCP service data unit(PSDU) and regarding the radio frequency (RF), PHY, and MAC propertiesof a PPDU. Several sub-fields may be located either in the HE-SIG-Aand/or HE-SIG-B fields. In one aspect, the HE-SIG-A field can becarried/modulated using an FFT size of 64 on a 20 MHz basis. TheHE-SIG-B field can be carried/modulated using an FFT size of e.g., 64 or256 on a 20 MHz basis depending on implementation. The HE-SIG-A andHE-SIG-B fields may occupy the entire channel bandwidth of the frame. Insome aspects, the size of the HE-SIG-A field and/or the HE-SIG-B fieldis variable. In other words, the number of symbols contained in theHE-SIG-A field and/or HE-SIG-B field can vary from frame to frame. AnHE-SIG-B field is not always present in all frames. In some cases,single user (SU) packets and UL trigger-based packets do not contain theHE-SIG-B field. To facilitate decoding of the HE frame 600 by areceiver, the size of (e.g., number of symbols contained in) theHE-SIG-B field may be indicated in the HE-SIG-A field. In some aspects,the HE header also includes a repeated L-SIG (RL-SIG) field, whosecontent is the same as the L-SIG field.

For a 20 MHz channel, an FFT size of 64 is associated with a discreteFourier transform (DFT) period of 3.2 μs and a subcarrier spacing of312.5 kHz. For a 20 MHz channel, an FFT size of 256 is associated with aDFT period of 12.8 μs and a subcarrier spacing of 78.125 kHz. The DFTperiod may also be referred to as an inverse DFT period (IDFT) or anIDFT/DFT period. The DFT period may be denoted as T_(DFT). Thesubcarrier spacing may be referred to as a subcarrier frequency spacingand may be denoted as Δ_(F). The subcarrier spacing may be obtained bydividing the channel bandwidth by the FFT size. The subcarrier spacingis the reciprocal of the DFT period.

The HE header may further include HE-STF and HE-LTF fields, whichcontain symbols used to perform necessary RF and PHY processing for eachPSDU and/or for the whole PPDU. The HE-LTF symbols may bemodulated/carried with an FFT size of 256 for 20 MHz bandwidth andmodulated over the entire bandwidth of the frame. Thus, the HE-LTF fieldmay occupy the entire channel bandwidth of the frame. In one aspect, anHE-LTF sequence may be utilized by a receiver to estimate MIMO channelbetween the transmitter and the receiver. Channel estimation may beutilized to decode data transmitted and compensate for channelproperties (e.g., effects, distortions). For example, when a preamble istransmitted through a wireless channel, various distortions may occur,and a training sequence in the HE-LTF field is useful to reverse thedistortion. This may be referred to as equalization. To accomplish this,the amount of channel distortion is measured. This may be referred to aschannel estimation. In one aspect, channel estimation is performed usingan HE-LTF sequence, and the channel estimation may be applied to otherfields that follow the HE-LTF sequence.

The HE-STF symbols may have a fixed pattern and a fixed duration. Forexample, the HE-STF symbols may have a predetermined repeating pattern.In one aspect, the HE-STF symbols do not require FFT processing. The HEframe 600 may include the data field, represented as HE-DATA, thatcontains data symbols. The data field may also be referred to as apayload field, data, payload, PSDU, or Media Access Control (MAC)Protocol Data Units (MPDU) (e.g., MAC frame).

In one or more aspects, additional one or more HE-LTF fields may beincluded in the header. For example, an additional HE-LTF field may belocated after a first HE-LTF field. The HE-LTF fields may be, forexample, modulated/carried with FFT size of 64 on a 20 MHz channel andmay be included as part of the first part of the HE frame 600. In one ormore implementations, a TX signal processing unit 280 (or an IFT 284)illustrated in FIG. 3A may carry out the modulation described in thisparagraph as well as the modulations described in other paragraphsabove. In one or more implementations, an RX signal processing unit 290(or an FT 292) may perform demodulation for a receiver.

FIG. 7 illustrates a schematic diagram of an example of an exchange offrames among wireless communication devices for MU transmission. An MUtransmission may be, for example, MU-MIMO or OFDMA. A UL MU PPDU may bea UL MU-MIMO PPDU or a UL OFDMA PPDU. The horizontal dimension in FIG. 7represents the time dimension. The wireless communication devicesinclude an AP, a participating STA1, a participating STA2, and aparticipating STA n. Although FIG. 7 illustrates an exchange of framesbetween an AP and three stations participating in an MU transmission,the exchange of frames may be between the AP and fewer than or greaterthan three stations, including the exchange of frames between the AP andone participating station (e.g., a non-OFDMA case).

In FIG. 7, the AP sends a trigger frame 710 to a group of stations(e.g., STA1, STA2, and STA n). The trigger frame 710 may occupy theentire channel bandwidth over which DL MU (e.g., OFDMA) transmissionoccurs. By way of non-limiting example, the entire channel bandwidthover which DL transmission occurs may be 20 MHz, 40 MHz, 80 MHz, or 160MHz. The trigger frame 710 may provide, for example, a transmissionopportunity (TXOP) to the participating stations and may indicateresource allocation information for the participating stationspertaining to MU transmission. The trigger frame 710 may indicate theTXOP duration. The TXOP duration may be an interval/duration of timeduring which the participating stations have the right to initiate frameexchange sequences onto the wireless medium. In an aspect, within theTXOP duration, the trigger frame 710, one or more uplink frames (e.g.,720, 730, 740, 750), and/or one or more downlink frames (not shown) maybe sent between the AP and the participating stations. In an aspect, theTXOP duration may include the transmission time of the trigger frame710.

The resource allocation information may include a sub-band (or afrequency subchannel) assigned to each respective one of theparticipating stations. For instance, when there are two stations, andthe uplink channel bandwidth is, for example, 80 MHz, then the AP mayassign a sub-band of the uplink channel bandwidth (e.g., a portion of 80MHz) to each respective station so that each station has its assignedsub-band. In some aspects, the resource allocation information may alsoinclude scheduling information regarding when a respective one of theparticipating stations may transmit using its assigned sub-band, and/ormay include the number of spatial streams that the stations may use.

In some aspects, the trigger frame 710 may include per user information(Per User Info) fields, where each station is associated with one of thePer User Info fields. For example, STA1 may be associated with the PerUser Info 1 field, STA2 may be associated with the Per User Info 2field, and so forth. A User Identifier field and a Resource Unit (RU)Allocation field of each Per User Info field may indicate an associationidentifier (AID) of the station associated with the Per User Info fieldand the station's allocated RU for use in transmitting the MPDU(s) inthe HE trigger-based PPDU. A Spatial Steam (SS) Allocation field of eachPer User Info field may indicate the spatial streams of the HEtrigger-based PPDU response to the station identified by the UserIdentifier field.

When the participating stations receive the trigger frame 710 sent bythe AP, the participating stations may decode the trigger frame 710 andidentify the frequency sub-bands allocated to the participatingstations. The participating stations may transmit uplink frames as partof UL OFDMA transmission to the AP. In this regard, each of STA1, STA2,and STA n may transmit an uplink frame 720, 730, and 740, respectively,that includes a header and a payload. The uplink frames 720, 730, and740 may be referred to as UL MU PPDUs. By way of non-limiting example,the entire channel bandwidth over which UL OFDMA transmission occurs maybe 20 MHz. 40 MHz, 80 MHz, or 160 MHz.

In some aspects, the header of the uplink frames 720, 730, and 740 maybe identical to each other. The header (or at least a portion of theheader) of the uplink frames 720, 730, and 740 may occupy the entirechannel bandwidth supported by the UL OFDMA transmission (or the UL MUtransmission). The header may include a legacy header. In an aspect, theheader may include a legacy header and some or all fields of anon-legacy header (e.g., an HE header). In another aspect, the header(or at least a portion of the header) of the uplink frames 720, 730, and740 may occupy only one or more 20 MHz channel bandwidths within whichthe payload (e.g., HE-DATA field) is transmitted. In one or moreaspects, the header of the frame may correspond to the preamble of PPDUaccording to the IEEE 802.11 standard. For instance, the header/preambleof the uplink frames 720, 730, and 740 may include a legacy header and anon-legacy header, such as described above, for example, with respect tothe HE frame 600 of FIG. 6.

The payload of the uplink frames 720, 730, and 740 may be a PSDU (or anHE-DATA field of the frame 600) that occupies a frequency sub-band. InFIG. 7, the payload (e.g., HE-DATA field) of the participating STA1,STA2, and STA n are represented by Data 1, Data 2, and Data n,respectively, and may occupy a respective frequency sub-band assigned toeach participating station.

After the stations transmit their respective uplink frame 720, 730, and740, the uplink frames 720, 730, and 740 may be combined (or aggregated)to form a single combined frame 750, which is received by the AP. Asingle combined frame may be referred to as an air-combined frame, anaggregated frame, a combined UL frame, a final UL frame, an MU frame, aUL MU frame, a UL OFDMA frame, or a variant/combination thereof (e.g.,an air-combined UL frame). The payload associated with eachparticipating station is frequency multiplexed in the single combinedframe 750. In an aspect, the HE trigger-based PPDU response may includeand/or may refer to the uplink frames 720, 730, and 740, and/or thesingle combined frame 750.

It is noted that FIG. 7 depicts a portion of the trigger frame 710,uplink frames 720, 730, and 740, and single combined frame 750. Forexample, in FIG. 7, for the uplink frame 720, the L-SIG field of thelegacy header, the SIG-A (HE-SIG-A) field of the non-legacy header, andthe payload are shown. The ellipses before the L-SIG field and after theSIG-A (HE-SIG-A) field may indicate one or more additional fields priorto the L-SIG field and after the SIG-A (HE-SIG-A) field, respectively.The ellipses between the uplink frames 730 and 740 may indicate one ormore additional uplink frames or no uplink frames between the uplinkframes 730 and 740. In an aspect, the L-SIG field shown in the frames710, 720, 730, 740, and 750 may be the RL-SIG (Repeated L-SIG) field.

As shown in FIG. 7, in some aspects, in an UL MU PPDU (e.g., 720, 730,740), information in the L-SIG field and SIG-A field may beair-combined. Thus, in some aspects, the AP shall send a trigger frame(e.g., 710) to the participating stations, and the participatingstations, upon receipt of the trigger frame, may form the UL MU preamble(e.g., UL MU header) of the UL MU PPDU based on the contents of thetrigger frame. In other words, the contents of the trigger frame may beused to form/derive the UL MU preamble. For example, the participatingstations may derive the UL MU preamble based on the contents of thetrigger frame and/or copy the contents of the trigger frame into fields(e.g., L-SIG field, SIG-A field) of the UL MU preamble.

In some cases, therefore, the AP may know all the informationpotentially contained in the L-SIG and SIG-A fields in the UL MU PPDUsfrom the participating stations. In such cases, since the AP alreadyknows the content of the L-SIG field and the HE-SIG-A field of the UL MUPPDUs prior to receiving the UL MU PPDUs, it may be redundant to includethe information in the valuable preamble portion of the UL MU PPDUs. Asthe AP already knows the content of the L-SIG field and the HE-SIG-Afield of the UL MU PPDUs, the AP's trigger frame may contain the contentassociated with a L-SIG field of a UL MU PPDU (L-SIG information) andthe content associated with an HE-SIG-A field of a UL MU PPDU (SIG-Ainformation), and a STA may generate its uplink frame having the L-SIGfield and the HE-SIG-A field, where the uplink frame's L-SIG field isprovided based on the L-SIG information contained in the trigger frame,and the uplink frame's HE-SIG-A field is generated based on the SIG-Ainformation contained in the trigger frame.

In one or more implementations, the preamble (e.g., L-SIG and SIG-A)structure in the UL MU PPDUs may be designed with the following traits:

-   -   L-SIG field and SIG-A field are air-combined, and thus all        contents from the participating UL MU stations should be the        same;    -   L-SIG field should be understood by legacy stations (e.g., IEEE        802.11 a, b, g, n, and ac stations);    -   SIG-A is more valuable if it can be understood by third party        stations.

FIG. 8 illustrates a schematic diagram of an example of an exchange offrames among wireless communication devices for MU transmission. Thehorizontal dimension in FIG. 8 represents the time dimension. An AP maysend a trigger frame 810 to participating stations STA1, STA2, and STAn, and the participating stations STA1, STA2, and STA n may transmituplink frames 820, 830, and 840, respectively, to the AP in response tothe trigger frame 810. In an aspect, the uplink frames 820, 830, and 840are combined to form a single combined UL frame, which is received bythe AP. In an aspect, the frames 810, 820, 830, 840, and the combined ULframe may be, may include, or may be a part of, the frames 710, 720,730, 740, 750, respectively. It is noted that the ellipses between theuplink frames 830 and 840 may indicate one or more additional uplinkframes or no uplink frames between the uplink frames 830 and 840.

In one or more aspects, in the case of the L-SIG field in the UL MUPPDUs (e.g., the uplink frames 820, 830, and 840), the legacy L-SIGformat may be reused. The legacy L-SIG format is utilized in other IEEE802.11 specifications, including, for example, the IEEE 802.11 a, b, g,n, and ac specifications. Reuse of the legacy L-SIG field in the UL MUPPDU may facilitate compatibility with the legacy devices and allow thelegacy stations (e.g. non-HE stations) to understand the L-SIG field ofthe HE trigger-based based UL MU PPDUs. In the legacy L-SIG format, theL-SIG field may include a RATE field and a LENGTH field. In an aspect,an HE station may set (e.g., pre-define) the RATE subfield of the L-SIGfield to 6 Mbps and derive a value of the LENGTH field of the L-SIGfield that indicates the time duration of the UL MU PPDU. The LENGTHfield may include a spoofed length (e.g. in bytes) such that when anyreceiver of the UL MU PPDU (e.g., the AP) calculates the length of theUL MU PPDU, the computed length matches the time duration required forthe UL MU PPDU.

With reference to FIG. 8, the trigger frame 810 may include a valueLENGTH_1 in its L-SIG field that is indicative of a transmission timefor transmitting the trigger frame 810. In an aspect, the value LENGTH_1may be contained in the LENGTH field of the L-SIG field of the triggerframe 810. The trigger frame 810 may also include a DURATION. As shownin FIG. 8, the DURATION may correspond to a time duration from the endof the trigger frame 810 until the end of the UL MU PPDU. In an aspect,the DURATION indicated by the trigger frame 810 may be based on alongest UL MU PPDU to be transmitted by a participating station inresponse to the trigger frame 810. In other words, the DURATION may bebased on a longest UL MU PPDU of the UL MU PPDUs to be received (e.g.,received simultaneously) by the AP. In the case that a TXOP durationaccording to the IEEE 802.11 standard ends at the same time as the endof the UL MU PPDU, the DURATION may be the same as the TXOP duration.

Each of the uplink frames 820, 830, and 840 may include a value LENGTH_2in its L-SIG field (e.g., LENGTH in the L-SIG field) that is indicativeof a transmission time for transmitting the uplink frames 820, 830, and840. The LENGTH in the L-SIG field of an uplink frame can be derivedfrom the associated trigger frame. For example, the value LENGTH_2 inthe L-SIG field of the uplink frames 820, 830, and 840 may be based on(e.g., derived from) the information in the associated trigger frame810. In one example, the value LENGTH_2 of the uplink frames 820, 830,and 840 may be calculated using the DURATION indicated by the triggerframe 810. For example, the value LENGTH_2 contained in the L-SIG fieldof the uplink frames 820, 830, and 840 may be the DURATION indicated bythe trigger frame 810 minus SIFS. In an aspect, the SIFS may representan interval for a receiver to decode data and to transmit anacknowledgement (ACK). For example, the SIFS may be 16 microseconds. Inan aspect, the DURATION indicated by the trigger frame 810 can be basedon the longest UL MU PPDU. For example, in FIG. 8, the longest UL MUPPDU is the uplink frame 830. In an aspect, the other UL MU PPDUs (e.g.,the uplink frames 820 and 840) may include padding in their respectivepayloads to extend the length of the UL MU PPDUs to the lengthassociated with the longest uplink frame (e.g., the uplink frame 830).

In one or more aspects, LENGTH_1 may be referred to as a transmissiontime (TXTIME) of the trigger frame 810, and LENGTH_2 may be referred toas a TXTIME of an uplink frame 820, 830, or 840. In one or more aspects,the trigger frame 810 may include LENGTH_2. For example, the valueLENGTH_2 may be included in the payload of the trigger frame 810, suchas in a Media Access Control (MAC) frame of the trigger frame 810. TheLENGTH in the L-SIG field of an uplink frame (e.g., 820, 830, 840) canbe derived (e.g., copied) from LENGTH_2 in the payload of the triggerframe 810.

FIG. 9 illustrates a schematic diagram of an example of an exchange offrames among wireless communication devices for MU transmission. Thehorizontal dimension in FIG. 9 represents the time dimension. An APsends a trigger frame 910, represented as A, to a group of participatingstations. The group of participating stations may send an uplink frameto the AP in response to the trigger frame 910. In an aspect, thetrigger frame 910 may be the trigger frame 710 of FIG. 7.

The trigger frame 910 may include a value associated with (e.g.,indicative of) a transmission time (TXTIME) of the trigger frame 910,represented as TXTIME of A. The TXTIME of the trigger frame 910 may bethe time (e.g., in microseconds) required to transmit the trigger frame910.

A value may be, or may be based on, the TXTIME of a frame (e.g., aTXTIME of a DL or UL frame). In an aspect, a value associated with theTXTIME of a frame may be L_(LENGTH), whose value is based on the TXTIMEof the frame. For example,

${L_{LENGTH} = {{\lceil \frac{{TXTIME} - 20}{4} \rceil \times 3} - 3 - m}},{m = {1\mspace{14mu} {or}\mspace{14mu} 2}}$

In this example, the L_(LENGTH) provides a length associated with apredetermined portion of a frame. A predetermined portion may be, forexample, the portion of a frame (e.g., 910 or 920) after the end of theL-SIG field of the frame. Thus, in this example, the TXTIME of a framehas a one-to-one mapping with the L_(LENGTH). In an aspect, m=1 when atrigger frame (e.g., 910) is sent in an HE MU PPDU format and m=2 when atrigger frame is sent in an HE extended range SU PPDU format. In anaspect, in a legacy format (e.g., IEEE 802.11a, n, ac), m may be 0.

The value indicative of the TXTIME of the trigger frame 910 (e.g.,L_(LENGTH)) may be contained in a preamble of the trigger frame 910. Inan aspect, the value may be contained in the L-SIG field of the triggerframe 910. For example, the value may be contained as the LENGTH in theL-SIG field. In an aspect, both the TXTIME and the L_(LENGTH) of thetrigger frame 910 may be considered and referred to as a length of thetrigger frame 910 for simplicity. Similarly, for an uplink frame (e.g.,920), the TXTIME and the L_(LENGTH) of an uplink frame may be consideredand referred to as a length of the uplink frame for simplicity.

In one or more aspects, the trigger frame 910 may include valuesindicative of a remaining TXOP duration (e.g., a TXOP duration remainingafter transmission of the trigger frame 910) and TXTIME of a respondinguplink frame 920, represented as Length 1 and TXTIME of B, respectively.The responding uplink frame 920, represented as B, may represent one ormore uplink frames or a combined uplink frame (see, e.g., 720, 730, 740,or 750 in FIG. 7) transmitted by one or more participating stations tothe AP in response to the trigger frame 910. The uplink frame 920 mayalso be referred to as a responding UL MU PPDU or an HE trigger-basedPPDU.

The TXTIME of the uplink frame 920 may be the time (e.g., inmicroseconds) required by the group of stations to transmit the uplinkframe 920. In an aspect, the TXTIME for each station to transmit itsrespective uplink frame may be the same. In this aspect, the TXTIME ofthe uplink frame 920 indicated by the trigger frame 910 can be based onthe longest uplink frame from the group of stations, and the remaininguplink frames may include padding in their respective payloads to extendtheir length to the length associated with the longest uplink frame. Inan aspect, the Length 1 and TXTIME of B (or their representations) maybe included in a payload of the trigger frame 910. The Length 1 andTXTIME of B (or their representations) may be included in a MAC framecontained in the payload of the trigger frame 910. In an aspect, alength of an uplink frame (e.g., TXTIME of B or L_(LENGTH) of the uplinkframe, which is a representation of TXTIME of B) may be included in acommon information (Common Info) field of the trigger frame 910.

In some aspects, the uplink frame 920 may include a value indicative ofthe TXTIME of the uplink frame 920, represented as TXTIME of B. Forexample, the value may be a length of the uplink frame 920, which may bethe TXTIME of B or an L_(LENGTH) based on the TXTIME of B. The value maybe included in a preamble (e.g., L-SIG field) of the uplink frame 920.In some aspects, the value may be based on (e.g., derived from, copiedfrom) the corresponding value in the trigger frame 910. The TXTIME ofthe uplink frame 920 may be the same as the TXTIME of the uplink framestransmitted by each of the stations, which may be combined (e.g.,air-combined) to form a combined uplink frame. The payload of the uplinkframe 920 may include the payload from each of the group ofparticipating stations.

In some aspects, the uplink frame 920 may include a value (representedas Length 2 in FIG. 9) indicative of a remaining TXOP duration (e.g., aTXOP duration remaining from the end of transmission of the uplink frame920). The value (represented as Length 2) may be based on (e.g., derivedfrom) the content contained in the trigger frame 910. In an aspect, thestations may compute Length 2 based on Length 1 and TXTIME of B (ortheir representations) contained in the trigger frame 910. As anexample, Length 2=Length 1−Length of B, where TXTIME of B=Length ofB−SIFS. In an aspect, the value Length 2 may be contained in a preamble(e.g., HE-SIG-A field) of the uplink frame 920. For example, the valueLength 2 may be contained in a TXOP Duration field of the HE-SIG-Afield. In an aspect, the value Length 2 may be included in a payload ofthe uplink frame 920 in addition to being included in the preamble. Forexample, the value Length 2 may be included in a MAC frame contained inthe payload of the uplink frame 920. In an aspect, the Length 1 andLength 2 may be referred to as a (i) TXOP duration indicating theremaining time in the current TXOP, (ii) a remaining TXOP duration, or(iii) a TXOP duration for simplicity. For example, the Length 1 may be aTXOP duration remaining after transmission of a trigger frame (e.g.,910) or a TXOP duration remaining from the end of transmission of atrigger frame. Similarly, the Length 2 may be a TXOP duration remainingafter transmission of an uplink frame (e.g., 920) or a TXOP durationremaining from the end of transmission of an uplink frame.

As shown in FIG. 9, within the remaining TXOP duration (e.g., Length 2),a downlink frame 930 may be sent from the AP to one or moreparticipating stations and an uplink frame 940 may be sent from one ormore participating stations to the AP. In an aspect, similar to thetrigger frame 910, the downlink frame 930 may include a value indicativeof a TXOP duration remaining from the end of transmission of thedownlink frame 930 (e.g., in the payload of the downlink frame 930) anda TXTIME (or L_(LENGTH)) of the uplink frame 940 (e.g., in the payloadof the downlink frame 930). Similar to the uplink frame 920, the uplinkframe 940 may include a value indicative of any TXOP duration remainingfrom the end of transmission of the uplink frame 940 (e.g., in the SIG-Afield of the uplink frame 940) and a TXTIME (or L_(LENGTH)) of theuplink frame 940 (e.g., in the L-SIG field of the uplink frame 940). Theuplink frame 940 may be a combined (e.g., air-combined) frame formed ofuplink frames from multiple participating stations.

In one or more implementations, since the header of UL MU PPDUs (e.g.,720, 730, 740 of FIG. 7), which may include a legacy header and anon-legacy header, from each participating station contains identicalinformation (e.g., to allow air-combining), the header of the UL MUPPDUs does not contain information associated with decoding of anyparticular UL MU PPDU. In other words, the header of each UL MU PPDUdoes not include station specific content for decoding its payload. Inthis aspect, third party stations may be unable to decode the payload ofthe UL MU PPDU. In a case in which only the payload contains the TXOPduration information, the third party stations may be unable to accessthis information since the third party stations do not have informationto decode the UL MU PPDUs. Setting content associated with TXOP durationin the preamble of the downlink and/or uplink frames may facilitateaccess of the third party stations to the TXOP duration and allow thirdparty stations to evaluate availability of the AP. In an aspect,evaluating the availability of the AP may facilitate reduction ofinterference of the third party stations with any currently ongoingtransmissions.

In one or more aspects, for the SIG-A (HE-SIG-A) field in UL MU PPDUs(e.g., the uplink frames 720, 730, and 740 of FIG. 7), three approachescan be considered as follows:

-   -   Example of a first approach: SIG-A in UL MU PPDUs is a copy of        that SIG-A in the trigger frame        -   Full contents can be used for SIG-A validation, but it can            be too many bits for validity check    -   Example of a second approach: New SIG-A format        -   Some essential information which is helpful to other STAs,            etc.;        -   An indication bit is included in UL MU SIG-A, and it should            be also included in non-UL MU SIG-A in the same bit position            for a receiver to distinguish between two formats; and/or        -   The indication bit differentiates between UL MU PPDU and SU            PPDU.    -   Example of a third approach: Reuse Compressed MAC (CMAC) in IEEE        802.11ah, which is incorporated herein in its entirety.        -   Type of CMAC should be signaled by the AP (e.g., additional            indication bits are needed in the trigger frame (non-UL MU            preamble))        -   The indication bits can be multiple bits, and similar to the            second approach; those bit positions should be the same as            those in the non-UL MU SIG-A

In one or more implementations of the second approach, a duration to seta network allocation vector (NAV) for third party HE STAs should beincluded in UL MU PPDUs to protect in time-domain. In one or moreaspects, the duration should be included in the SIG-A field of the UL MUPPDUs. The duration included in the SIG-A field of the UL MU PPDUs canbe, or can be calculated from, a transmission opportunity (TXOP)duration of the current UL MU transmission. In an aspect, the durationis a TXOP duration (e.g., Length 2 of FIG. 9). A single transmission andACK pair or multiple transmission pairs may exist within the TXOPduration. Within the TXOP duration, transmission(s) may occur from theAP to the participating stations, and vice versa. In an aspect, theduration included in the UL MU HE-SIG-A, represented as DURATION_(UL)_(_) _(MU), can be calculated as follows:

-   -   DURATION_(UL) _(_) _(MU)=DURATION_(UL) _(_) _(MU) _(_)        _(Trigger)−LENGTH_(UL) _(_) _(MU) _(_) _(PPDU)        -   DURATION_(UL) _(_) _(MU) _(_) _(Trigger): Duration included            in the MAC header of the trigger frame corresponding to the            transmitting UL MU PPDU        -   LENGTH_(UL) _(MU) _(_) _(PPDU): Length of the transmitting            UL MU PPDU            The DURATION_(UL) _(_) _(MU) may provide a remaining TXOP            duration (e.g., a TXOP duration remaining from the end of            transmission of the associated uplink frame). As an example,            with reference to FIG. 9, the DURATION_(UL) _(_) _(MU) _(_)            _(Trigger), LENGTH_(UL) _(_) _(MU) _(_) _(PPDU), and            DURATION_(UL) _(_) _(MU) may be Length 1, Length of B, and            Length 2, respectively. In one example, DURATION_(UL) _(_)            _(MU) _(_) _(Trigger) may be DURATION shown in FIG. 8.

In an aspect, all times (e.g., Length 1, Length 2, TXTIME of A, etc.)can be calculated in microseconds. If a calculated duration includes afractional microsecond, the value inserted in the duration fields (e.g.,Length field, TXOP duration field) may be rounded up to the next higherinteger. If a calculated duration results in a negative value, the valueof the Duration/ID field is 0.

In one or more implementations of the second and third approaches,stations may need to know whether a PPDU is a downlink frame or anuplink OFDMA/MU-MIMO frame. In some aspects, the frame format can beeither indicated in HE-SIG-A field or determined by the modulation ofthe signal in an HE-SIG-A field.

In some aspects, UL MU PPDUs may utilize a different frame format andcontain different content from SU PPDUs and downlink MU PPDUs. In anaspect, the uplink SU PPDUs may share the same frame format as downlinkSU PPDUs. In SU PPDUs and downlink MU PPDUs, the preamble of these PPDUsmay contain content utilized in decoding the payload of these PPDUs. Forexample, the preamble may contain content in the L-SIG field, SIG-Afield, and/or SIG-B field, among other fields, to allow the decoding ofthe payload. In an aspect, in the case of UL MU PPDUs, the preamble ofthe UL MU PPDUs from each participating station in the UL MUtransmission is the same (e.g., to allow air-combining). In this regard,the UL MU PPDUs may contain globally useful/common information but nostation-specific content for decoding the payloads of each UL MU PPDU.

In some aspects, the frame format may be included in a Format field ofthe HE-SIG-A field. In an aspect, the frame format may contain content(e.g., an indication bit) that can be utilized to differentiate an SUPPDU and a trigger-based UL PPDU (e.g., UL MU PPDU). The indication bitmay be referred to as a format indication or a format bit. In an aspect,the frame format may contain content that may be utilized todifferentiate a UL MU PPDU from a non-UL MU PPDU. A non-UL MU PPDU mayinclude a UL SU PPDU, DL SU PPDU, and/or DL MU PPDU. In an aspect, theHE SU PPDU (e.g., HE DL SU PPDU, HE UL SU PPDU) and the HE trigger-basedUL PPDU may include the Format field.

FIG. 10 illustrates an example of utilization of a duration in UL MUPPDU transmissions. If a STA (represented as UL MU STA) involved in ULMU transmission sends a UL MU PPDU to the AP, and the preamble of the ULMU PPDU includes a duration in which the current UL MU transmission ismaintained (e.g., TXOP duration), three third party stations (e.g., HESTAs 1011, 1012, 1013) outside of the AP's coverage can be additionallyprotected on top of the third party stations inside of the AP's coverage(e.g., 1021, 1022, 1023, 1024). Accordingly, NAV can be set by thirdparty stations outside of the AP's coverage area.

In an aspect, to allow combining (e.g., air-combining) of the uplinkframes (e.g., 720, 730, 740 in FIG. 7), the preambles of the uplinkframes do not include station specific-content for decoding theirrespective payload. In this aspect, third party stations may be unableto decode the payloads of the uplink frames. Setting content associatedwith a TXOP duration in the preamble may facilitate access of the thirdparty stations to the TXOP duration. In an aspect, evaluating theavailability of the AP using the TXOP duration may facilitate reductionof interference of the third party stations with any currently ongoingor currently scheduled transmissions.

In one or more implementations, for the full protection of third partystations, the frequency domain may also be considered.

FIG. 11 illustrates an example of L-SIG field and SIG-A fieldtransmission in UL MU PPDU. In some cases, a station may transmit theL-SIG field and SIG-A field over an entire operating bandwidth (e.g., 40MHz), even though there is no assignment (e.g., no allocation) ofresources to the station in at least a portion of the operatingbandwidth. In FIG. 11, the station transmits the L-SIG field and theSIG-A field in the first 20 MHz frequency sub-band (see, e.g., 1110) ofthe 40 MHz operating bandwidth and in the second 20 MHz frequencysub-band (e.g., 1120) of the 40 MHz operating bandwidth, even though thestation is not allocated resources to transmit payload (e.g., HE-DATA)in the second 20 MHz frequency sub-band.

In some aspects, power saving may be achieved and implementationcomplexity may be reduced if the L-SIG field and the SIG-A field may besent in less than the entire operating bandwidth, such as in cases wherea station is not allocated resources for the entire operating bandwidth.For example, power saving may be achieved and implementation complexitymay be reduced since the station avoids having to change transmissionbandwidth during a transmission of a UL MU PPDU. In an aspect, UL MUTXOP is not fully protected in the frequency domain when the L-SIG fieldand the SIG-A field are not sent over the entire operating bandwidth.

FIG. 12 illustrates an example of an absolute frequency allocationinformation included in a SIG-A field of a UL MU PPDU. In an aspect, thechannel (frequency) information may be an absolute value or adistinguishable index because a third party station that receives asingle 20 MHz SIG-A can recognize the whole operating bandwidth for thecurrent UL MU transmission. In an aspect, with not sending L-SIG fieldand the SIG-A in frequency bands (e.g., 1220) in which there is no UL MUdata allocation (e.g., 1222), the operating bandwidth information (e.g.,absolute channel information) carried in SIG-A may facilitate protectionfrom third party stations. In an aspect, the minimum granularity can be20 MHz.

In the example shown in FIG. 12, the station transmits the L-SIG fieldand the SIG-A field in the first 20 MHz frequency sub-band (see, e.g.,1210) of the 40 MHz operating bandwidth where the station is allocatedresources to transmit a payload (e.g., HE-DATA). The station, however,does not transmit the L-SIG field and the SIG-A field in the second 20MHz frequency sub-band (e.g., 1220) of the 40 MHz operating bandwidth,where the station is not allocated resources to transmit a payload(e.g., HE-DATA).

The SIG-A in the UL MU PPDU may include multiple channel indices (e.g.,n and n+1) or a set of starting channel index (e.g., n) and bandwidthwhen continuous bandwidth is assumed. If non-contiguous bandwidthallocation is assumed (e.g., 80 MHz+80 MHz), an absolute value or adistinguishable index may be used, or multiple sets of starting channelindices and bandwidth may be used. The absolute frequency informationcan be beneficial to stations in overlapping basic service set (OBSS)even in the case shown in FIG. 11.

As another example, the L-SIG and SIG-A fields in a primary channel mayalways be transmitted even if there is no UL OFDMA data in the primarychannel, and L-SIG and SIG-A is transmitted in secondary channels whereUL OFDMA data is allocated. In this case, the absolute frequencyallocation information in SIG-A of UL MU PPDU may be useful.

In one or more implementations, the L-SIG and SIG-A fields, among otherfields in the preamble, are sent only in frequency bands within which ULOFDMA data is allocated. In an aspect, a minimum granularity for sendingthe L-SIG and SIG-A fields, among other fields in the preamble, may be20 MHz frequency bands. The UL OFDMA data may be carried over less thanan entirety of the frequency bands. In an aspect, the absolute channelinformation is not included in the preamble.

Based on the frequency allocation information and the assumption thatthe number of SIG-A symbols in a UL MU PPDU is 2, the SIG-A field mayhave the following design. The number of bits for each field of theSIG-A field is by way of non-limiting example. In this example, thenumber of total bits is 48 bits, which may exactly fit into 2 symbols ofSIG-A in 64 FFT transmission.

-   -   CRC (8 bits), Tail (6 bits)    -   UL MU Indication (1 bit)        -   Differentiate between UM MU (trigger-based UL MU)            transmission and SU transmission (downlink and uplink)        -   This indication should be located in the same bit position            of that in non-UL MU SIG-A (e.g., downlink and uplink SU            SIG-A)    -   Duration (16 bits)        -   TXOP duration for time-protection, informed by the            triggering AP        -   Unit of microsecond, and can be reduced depending on the            available bits    -   Partial basic service set identifier (BSSID) of the triggering        AP (9 bits)        -   Partial BSSID of the triggering AP is also necessary to            distinguish with other UL MU transmission.    -   Channel number, n_(ch,20) of 20 MHz bandwidth as a channel index        of starting 20 MHz from the lowest frequency (6 bits)        -   Because SIG-A is duplicated in every 20 MHz, a third party            station reading a SIG-A in 20 MHz cannot figure out the            whole operating bandwidth        -   In the unit of 20 MHz, n_(ch,20)=1, . . . , 50 can be enough            to indicate the exact position            -   Lowest 20 MHz channel frequency=channel starting                frequency+20×n_(ch,20) (MHz)                -   Note that in VHT specification, Channel center                    frequency=Channel starting frequency+5×n_(ch) (MHz),                    where n_(ch)=1, . . . 200, and it means 200 indices                    can express the whole channels of 5 MHz unit.                    Therefore, 50 indices are enough to indicate the                    whole bandwidth in the unit of 20 MHz    -   Bandwidth (2 bits)        In an aspect, the BSSID field may be referred to as a Color        field.

As another example, the SIG-A field may have the following design.

-   -   CRC (4 bits), Tail (6 bits)    -   UL MU Indication (1 bit)    -   Duration (7 bits)    -   Partial basic service set identifier (BSSID) of the triggering        AP (6 bits)    -   Bandwidth (2 bits)

The SIG-A field provided above are by way of non-limiting example. TheSIG-A field may be of a different size. In an aspect, for instance, theSIG-A field may be 52 bits.

In the third approach (e.g., reuse CMAC in IEEE 802.11ah), an indicationis also included in UL MU SIG-A and non-UL MU SIG-A in the sameposition. In an aspect, multiple bits may be used if multiple IEEE802.11ah CMAC frames are considered for UL MU PPDU. In an aspect, UL MUSIG-A may refer to the SIG-A field of a UL MU PPDU. In an aspect, non-ULMU SIG-A may refer to the SIG-A field of a non-UL MU PPDU.

In IEEE 802.11ah, there are two types of field formats depending on thebandwidth. Each field format has nine types of CMAC frames (3 bits forthe types).

-   -   8 control frames: null data packet (NDP) clear to send (CTS),        NDP contention-free end (CF-End), NDP power save-poll (PS-Poll),        NDP acknowledgement (Ack), NDP power save-poll acknowledgement        (PS-Poll-Ack), NDP block acknowledgement (BlockAck), NDP        Beamforming Report Poll, NDP Paging    -   1 management frame: NDP Probe Request

In order to allow reuse of existing CMAC frame, the following should beconsidered:

-   -   Some CMAC frames cannot be used if they include station specific        information (e.g., preferred modulation and coding scheme (MCS)        in NDP PS-Poll)    -   2 MHz NDP CMAC cannot be used in some frame types because CRC is        4 bits in IEEE 802.11ah but 8 bits in IEEE 802.11ax

In an aspect, each type of CMAC frame has two types depending on sub-1GHz (SIG) NDP frame format, except for the NDP Beamforming Report Pollwhich has only 2 MHz frame. The SIG NDP frame format may include anNDP_1M for a 1 MHz frame format and NDP_2M for a 2 MHz frame format.Each type of CMAC may include a Duration field and a RA/TA/Partial BSSIDfield. These fields are common to all nine types of CMAC frames and maybe referred to as common component fields. For NDP_1M, the Durationfield may be 10 bits referring to units of OFDM symbol duration (40 μs).For NDP_2M, the Duration field may be 15 bits referring to units ofmicroseconds in most cases. In an NDP_2M Ack, the Duration field may be14 bits. The Partial BSSID field, which contains a partial AID orpartial BSSID, may be 9 bits. In some aspects, one of the nine CMACframes may be used as the pre-defined UL MU preamble format. In someaspects, compared to the second approach, duration and RA is stillincluded, but no channel number is included.

FIG. 13 illustrates an example of a SIG field format for a 1 MHz nulldata packet (NDP) CMAC frame. FIG. 14 illustrates an example of a SIGfield format for a greater than or equal to 2 MHz NDP CMAC frame.

FIG. 15 illustrates an example of an NDP CTS frame. In an aspect, theNDP CTS frame may be an NDP_2M CTS frame. FIG. 16 illustrates an exampleof an NDP CF-End frame. In an aspect, the NDP CF-End frame may be anNDP_2M CF-End frame. The NDP CTS frame and NDP CF-End frame may includea CTS/CF-End Indicator field that indicates whether the frame is a CTSor CF-End frame. The CTS/CF-End Indicator field may be 1 bit (e.g.,binary). The Address Indicator field may be 1 bit. For example, theAddress Indicator field may be set to 0 to indicate that the RA/PartialBSSID field contains the partial identifier of the receiving station.The Address Indicator field may be set to 1 to indicate that theRA/Partial BSSID field contains the partial BSSID of the AP transmittingthe frame and is interpreted as a broadcast address. The Early SectorIndicator field may be utilized to indicate if the NDP CTS frame isfollowed by the sectorized beam frame exchange. The Early SectorIndicator field may be 1 bit.

In an aspect, the NDP CTS frame format may be used without the fourreserved bits. The first 33 bits may be utilized, followed by 1 bit fora UL MU indication (e.g., for third party stations) and 14 bits for aCRC/Tail. The modified NDP CTS frame format may be 48 bits.

FIG. 17 illustrates an example of an NDP PS-Poll frame. In an aspect,the NDP PS-Poll frame may be an NDP_2M PS-Poll frame. The Preferred MCSfield may be 3 bits for NDP_1M (e.g., 0˜6, MSC index, 7: no preference)and 5 bits for NDP_2m (e.g., 0˜9: MSC index, 10: no preference, 11˜15:reserved). The Uplink Data Indicator (UDI) field may be 1 bit for NDP_1Mor 12 bits for NDP_2M. For NDP_1M, the 1 bit may be utilized to indicateif the station has uplink data to transmit. For NDP_2M, the 12 bits maybe utilized to indicate if the station has uplink data to transmit andmay be utilized by a subchannel selective transmission (SST) station toindicate its SST channel. For example, the UDI field may be set to 0 toindicate there is no uplink data to be sent: set to 1 to indicate thereis uplink data to be sent; set between 2 and 9 to indicate relativeposition of the selected SST channel; and set to 10 or greater toindicate the estimated time, in units of 40 μs, required for uplink dataframes that are present at the station, excluding the duration of theirresponse and applicable IFS durations.

FIG. 18 illustrates an example of an NDP Ack frame. In an aspect, theNDP Ack frame may be an NDP_2M Ack frame. FIG. 19 illustrates an exampleof an NDP PS-Poll-Ack frame. In an aspect, the NDP PS-Poll-Ack frame maybe an NDP_2M PS-Poll-Ack frame. The Ack ID field may be 9 bits or 16bits. The Ack ID field may be set to the bit sequence CRC[0:3]∥TA[4:8]or CRC[0:3]∥TA[0:8]∥RA[6:8] obtained from the CRC, TA, and RA field ofthe NDP PS-Poll frame that elicited the response. The Idle Indicationfield may be 1 bit, and may be set to 1 if the Duration field indicatesan idle period. The Relayed Frame field and the More Data field may eachbe 1 bit.

FIG. 20 illustrates an example of an NDP BlockAck frame. In an aspect,the NDP BlockAck frame may be an NDP_2M BlockAck frame. The BlockAck IDfield may be 2 bits or 6 bits. The BlockAck ID field may contain the 2or 6 LSBs of the bit sequence of the scrambler initialization value inthe SERVICE field prior to the descrambling of the PSDU that carries thesoliciting frame. The Starting Sequence Control field may be 12 bits,and may contain the sequence number of the first MSDU or A-MSDU forwhich the NDP BlockAck frame is sent. The Block Ack Bitmap field may be8 or 16 bits. The Block Ack Bitmap field may indicate the receivedstatus of up to 8 or 16 MSDUs and A-MSDUs when the NDP BlockAck is usedduring a BlockAck session. Each bit that is set equal to 1 in the NDPBlockAck bitmap acknowledges the successful reception of a single MSDUor A-MSDU, in the order of sequence number. The Block Ack Bitmap fieldmay indicate the received status of up to 8 or 16 fragments of an MSDUwhen the NDP BlockAck is used during a fragment BA session. Each bitthat is set equal to 1 in the BlockAck bitmap acknowledges thesuccessful reception of a single fragment of an MSDU, in the order ofthe fragment number.

FIG. 21 illustrates an example of an NDP Beamforming Report Poll frame.In an aspect, the NDP Beamforming Report Poll frame may be an NDP_2MBeamforming Report Poll frame. The Feedback Segment RetransmissionBitmap field may indicate the feedback segments to be polled in aCompressed Beamforming report (e.g., VHT or HE compressed beamformingreport), which may be contained in one or more compressed beamformingframes (e.g., VHT or HE compressed beamforming frames). In an aspect,the Beamforming Report Poll frame is not utilized in NDP_1M.

FIG. 22 illustrates an example of an NDP Paging frame. In an aspect, theNDP Paging frame may be an NDP_2M Paging frame. The P-ID field mayinclude 9 bits and may be an identifier of the NDP paging requester. TheDirection field may be 1 bit. If the Direction field is 1, theAPDI/Partial AID field indicates AP direction information (APDI). If theDirection field is 0, the APDI/Partial AID field indicates the partialAID of the NDP paging responder station. The APDI field may be 9 bits.The 8 MSBs of the APDI, depending on the value of the Action subfield ofthe NDP Paging Response, contain:

-   -   The PTSF subfield if the Action subfield is not equal to 4. The        PTSF subfield is set to the value of the partial TSF of the        transmitting station as defined in Section 10.44.6 (NDP Paging        Setup) of IEEE 802.11ah draft v6.0.    -   The ASD subfield if the Action subfield is equal to 4. The ASD        subfield is the additional sleep duration and is set to the        time, in units of SIFS, after which the receiver station is in        Awake state as described in Section 10.44.6 (NDP Paging Setup)        of IEEE 802.11ah.        The LSB of the APDI is the Check Beacon Flag subfield and is an        indicator of critical changes in the Beacon frame as described        in Section 10.44.6 (NDP Paging Setup) of IEEE 802.11ah.

FIG. 23 illustrates an example of an NDP Probe Request frame. In anaspect, the NDP Probe Request frame may be an NDP_2M Probe Requestframe. The CSSID/ANO Present field may be 1 bit. The CSSID/ANO Presentfield may indicate if the NDP Probe Request frame contains a CompressedSSID field or an Access Network Option field. The CSSID/ANO Presentfield may be set to 0 if the NDP Probe Request contains the CompressedSSID, and may be set to 1 if the NDP Probe Request contains the AccessNetwork Option. The Compressed SSID/ANO Option may be 16 or 32 bits. TheCompressed SSID/Access Network Option [0:31] may be set to CompressedSSID, which may be a 32-bit CRC calculated as defined in Section 9.2.4.8(FCS field) of IEEE 802.11ah draft v6.0, wherein the calculated fieldsis the full SSID. The Compressed SSID/Access Network Option [0:7] may beset to Access Network Option, which is defined in Section 9.4.2.92(Interworking element) of IEEE 802.11ah (see FIG. 9-436 (Access NetworkOptions field format)). Compressed SSID/Access Network Option[8:31] maybe reserved. The Requested Probe Request Response Type field may be 1bit. The Requested Probe Request Response Type field may be set to 0 ifthe station requests a Short Probe Response frame, and may be set to 1if the station requests a Probe Response frame.

In FIGS. 13 through 23, the bits associated with each field of the frameis provided. For example, in FIG. 16, the NDP CMAC Frame Type field iscontained in bits B0 through B2 of the NDP CF-End frame. In other words,the NDP CMAC Frame Type field forms the first 3 bits of the NDP CF-Endframe.

It should be noted that like reference numerals may designate likeelements. These components with the same reference numerals have certaincharacteristics that are the same, but as different figures illustratedifferent examples, the same reference numeral does not indicate that acomponent with the same reference numeral has the exact samecharacteristics. While the same reference numerals are used for certaincomponents, examples of differences with respect to a component aredescribed throughout this disclosure.

FIGS. 24A, 24B, and 24C illustrate flow charts of examples of methodsfor facilitating wireless communication. For explanatory andillustration purposes, the example processes 2410, 2420 and 2430 may beperformed by the wireless communication devices 111-115 of FIG. 1 andtheir components such as a baseband processor 210, a MAC processor 211,a MAC software processing unit 212, a MAC hardware processing unit 213,a PHY processor 215, a transmitting signal processing unit 280 and/or areceiving signal processing unit 290; however, the example processes2410, 2420 and 2430 are not limited to the wireless communicationdevices 111-115 of FIG. 1 or their components, and the example processes2410, 2420 and 2430 may be performed by some of the devices shown inFIG. 1, or other devices or components. Further for explanatory andillustration purposes, the blocks of the example processes 2410, 2420and 2430 are described herein as occurring in serial or linearly.However, multiple blocks of the example processes 2410, 2420 and 2430may occur in parallel. In addition, the blocks of the example processes2410, 2420 and 2430 need not be performed in the order shown and/or oneor more of the blocks/actions of the example processes 2410, 2420 and2430 need not be performed.

Various examples of aspects of the disclosure are described below asclauses for convenience. These are provided as examples, and do notlimit the subject technology. As an example, some of the clausesdescribed below are illustrated in FIGS. 24A, 24B and 24C.

Clause A. An access point for facilitating multi-user communication in awireless network, the station comprising: one or more memories; and oneor more processors coupled to the one or more memories, the one or moreprocessors configured to cause: generating a trigger frame, the triggerframe comprising a first content and a second content, wherein the firstcontent is associated with a legacy signal (L-SIG) field of an uplinkframe, and the second content is associated with a non-legacy signalfield of the uplink frame, providing the trigger frame for transmission;receiving the uplink frame in response to the trigger frame, the uplinkframe comprising the L-SIG field and the non-legacy signal field,wherein a length in the L-SIG field of the uplink frame is based on thetrigger frame, and wherein a duration in the non-legacy signal field ofthe uplink frame is based on the trigger frame; and providing the uplinkframe for processing.

Clause B. A station for facilitating multi-user communication in awireless network, the station comprising: one or more memories; and oneor more processors coupled to the one or more memories, the one or moreprocessors configured to cause: receiving a trigger frame; generating anuplink frame based on the trigger frame, wherein the uplink framecomprises a legacy signal (L-SIG) field and a non-legacy signal field,wherein the L-SIG field comprises a length of the uplink frame, andwherein the non-legacy signal field comprises a remaining transmissionopportunity (TXOP) duration; and providing the uplink frame fortransmission, wherein the remaining TXOP duration is a TXOP durationremaining after transmission of the uplink frame.

Clause C. A computer-implemented method of facilitating multi-usercommunication in a wireless network, the method comprising: receiving atrigger frame; generating an uplink frame in response to the triggerframe, the uplink frame comprising a signal-A (SIG-A) field, wherein theSIG-A field comprises an indication whether the uplink frame uses anuplink multi-user (UL MU) frame format or a non-UL MU frame format,wherein the SIG-A field comprises information associated with atransmission opportunity (TXOP) duration, and wherein the information isgenerated based on a duration indicated in the trigger frame; andproviding the uplink frame for transmission.

In one or more aspects, additional clauses are described below.

A method comprising one or more methods or operations described herein.

An apparatus or a station comprising one or more memories (e.g., 240,one or more internal, external or remote memories, or one or moreregisters) and one or more processors (e.g., 210) coupled to the one ormore memories, the one or more processors configured to cause theapparatus to perform one or more methods or operations described herein.

An apparatus or a station comprising means (e.g., 210) adapted forperforming one or more methods or operations described herein.

A computer-readable storage medium (e.g., 240, one or more internal,external or remote memories, or one or more registers) comprisinginstructions stored therein, the instructions comprising code forperforming one or more methods or operations described herein.

In one aspect, a method may be an operation, an instruction, or afunction and vice versa. In one aspect, a clause may be amended toinclude some or all of the words (e.g., instructions, operations,functions, or components) recited in other one or more clauses, one ormore sentences, one or more phrases, one or more paragraphs, and/or oneor more claims.

To illustrate the interchangeability of hardware and software, itemssuch as the various illustrative blocks, modules, components, methods,operations, instructions, and algorithms have been described generallyin terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.Skilled artisans may implement the described functionality in varyingways for each particular application.

A reference to an element in the singular is not intended to mean oneand only one unless specifically so stated, but rather one or more. Forexample, “a” module may refer to one or more modules. An elementproceeded by “a,” “an,” “the,” or “said” does not, without furtherconstraints, preclude the existence of additional same elements.

Headings and subheadings, if any, are used for convenience only and donot limit the invention. The word exemplary is used to mean serving asan example or illustration. To the extent that the term include, have,or the like is used, such term is intended to be inclusive in a mannersimilar to the term comprise as comprise is interpreted when employed asa transitional word in a claim. Relational terms such as first andsecond and the like may be used to distinguish one entity or action fromanother without necessarily requiring or implying any actual suchrelationship or order between such entities or actions.

Phrases such as an aspect, the aspect, another aspect, some aspects, oneor more aspects, an implementation, the implementation, anotherimplementation, some implementations, one or more implementations, anembodiment, the embodiment, another embodiment, some embodiments, one ormore embodiments, a configuration, the configuration, anotherconfiguration, some configurations, one or more configurations, thesubject technology, the disclosure, the present disclosure, othervariations thereof and alike are for convenience and do not imply that adisclosure relating to such phrase(s) is essential to the subjecttechnology or that such disclosure applies to all configurations of thesubject technology. A disclosure relating to such phrase(s) may apply toall configurations, or one or more configurations. A disclosure relatingto such phrase(s) may provide one or more examples. A phrase such as anaspect or some aspects may refer to one or more aspects and vice versa,and this applies similarly to other foregoing phrases.

A phrase “at least one of” preceding a series of items, with the terms“and” or “or” to separate any of the items, modifies the list as awhole, rather than each member of the list. The phrase “at least one of”does not require selection of at least one item; rather, the phraseallows a meaning that includes at least one of any one of the items,and/or at least one of any combination of the items, and/or at least oneof each of the items. By way of example, each of the phrases “at leastone of A. B, and C” or “at least one of A, B, or C” refers to only A,only B, or only C; any combination of A, B, and C; and/or at least oneof each of A, B, and C.

It is understood that the specific order or hierarchy of steps,operations, or processes disclosed is an illustration of exemplaryapproaches. Unless explicitly stated otherwise, it is understood thatthe specific order or hierarchy of steps, operations, or processes maybe performed in different order. Some of the steps, operations, orprocesses may be performed simultaneously. The accompanying methodclaims, if any, present elements of the various steps, operations orprocesses in a sample order, and are not meant to be limited to thespecific order or hierarchy presented. These may be performed in serial,linearly, in parallel or in different order. It should be understoodthat the described instructions, operations, and systems can generallybe integrated together in a single software/hardware product or packagedinto multiple software/hardware products.

The disclosure is provided to enable any person skilled in the art topractice the various aspects described herein. In some instances,well-known structures and components are shown in block diagram form inorder to avoid obscuring the concepts of the subject technology. Thedisclosure provides various examples of the subject technology, and thesubject technology is not limited to these examples. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the principles described herein may be applied to otheraspects.

All structural and functional equivalents to the elements of the variousaspects described throughout the disclosure that are known or later cometo be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. §112, sixth paragraph, unless theelement is expressly recited using a phrase means for or, in the case ofa method claim, the element is recited using the phrase step for.

The title, background, brief description of the drawings, abstract, anddrawings are hereby incorporated into the disclosure and are provided asillustrative examples of the disclosure, not as restrictivedescriptions. It is submitted with the understanding that they will notbe used to limit the scope or meaning of the claims. In addition, in thedetailed description, it can be seen that the description providesillustrative examples and the various features are grouped together invarious implementations for the purpose of streamlining the disclosure.The method of disclosure is not to be interpreted as reflecting anintention that the claimed subject matter requires more features thanare expressly recited in each claim. Rather, as the following claimsreflect, inventive subject matter lies in less than all features of asingle disclosed configuration or operation. The following claims arehereby incorporated into the detailed description, with each claimstanding on its own as a separately claimed subject matter.

The claims are not intended to be limited to the aspects describedherein, but are to be accorded the full scope consistent with thelanguage claims and to encompass all legal equivalents. Notwithstanding,none of the claims are intended to embrace subject matter that fails tosatisfy the requirements of the applicable patent law, nor should theybe interpreted in such a way.

What is claimed is:
 1. An access point for facilitating multi-usercommunication in a wireless network, the station comprising: one or morememories; and one or more processors coupled to the one or morememories, the one or more processors configured to cause: generating atrigger frame, the trigger frame comprising a first content and a secondcontent, wherein the first content is associated with a legacy signal(L-SIG) field of an uplink frame, and the second content is associatedwith a non-legacy signal field of the uplink frame; providing thetrigger frame for transmission; receiving the uplink frame in responseto the trigger frame, the uplink frame comprising the L-SIG field andthe non-legacy signal field, wherein a length in the L-SIG field of theuplink frame is based on the trigger frame, and wherein a duration inthe non-legacy signal field of the uplink frame is based on the triggerframe; and providing the uplink frame for processing.
 2. The accesspoint of claim 1, wherein the length is based on the first content, andthe duration is based on the second content.
 3. The access point ofclaim 1, wherein the duration is information associated with atransmission opportunity (TXOP) duration.
 4. The access point of claim1, wherein the length of L-SIG field is based on a longest uplink frameamong uplink frames to be received simultaneously with the uplink frame.5. The access point of claim 1, wherein: the second content is a firsttransmission opportunity (TXOP) duration remaining after transmission ofthe trigger frame: the duration is a second TXOP duration remainingafter transmission of the uplink frame; and the second remaining TXOPduration is derived from the first remaining TXOP duration.
 6. Theaccess point of claim 1, wherein the non-legacy signal field of theuplink frame comprises an indication whether the uplink frame is in atrigger-based uplink (UL) frame format.
 7. The access point of claim 1,wherein the non-legacy signal field of the uplink frame comprises aformat indication bit to differentiate between a single user (SU) frameand an uplink multi-user (UL MU) frame, wherein the trigger frame is toinitiate UL MU frame transmission.
 8. The access point of claim 1,wherein the duration is to set a network allocation vector (NAV) by astation, wherein the station is not a destination of the uplink frame.9. The access point of claim 1, wherein the non-legacy signal field is ahigh efficiency signal-A (HE-SIG-A) field.
 10. The access point of claim1, wherein the first content comprises the length in the L-SIG field ofthe uplink frame.
 11. The access point of claim 1, wherein the firstcontent and the second content are located within a payload of thetrigger frame.
 12. A station for facilitating multi-user communicationin a wireless network, the station comprising: one or more memories; andone or more processors coupled to the one or more memories, the one ormore processors configured to cause: receiving a trigger frame;generating an uplink frame based on the trigger frame, wherein theuplink frame comprises a legacy signal (L-SIG) field and a non-legacysignal field, wherein the L-SIG field comprises a length of the uplinkframe, and wherein the non-legacy signal field comprises a remainingtransmission opportunity (TXOP) duration; and providing the uplink framefor transmission, wherein the remaining TXOP duration is a TXOP durationremaining after transmission of the uplink frame.
 13. The station ofclaim 12, wherein the non-legacy signal field comprises a formatindication bit to differentiate between a single user (SU) frame and anuplink multi-user (UL MU) frame, wherein the trigger frame is forinitiating UL MU frame transmission.
 14. The station of claim 12,wherein the non-legacy signal field further comprises an indicationwhether the uplink frame is in a trigger-based uplink (UL) frame format.15. The station of claim 12, wherein the length is based on a content inthe trigger frame.
 16. The station of claim 12, wherein the remainingTXOP duration is derived from a first remaining TXOP duration in thetrigger frame.
 17. The station of claim 12, wherein providing the uplinkframe for transmission comprises providing the L-SIG field and thenon-legacy signal field for transmission only in one or more frequencybands occupied by a payload of the uplink frame, wherein the minimumgranularity associated with each of the one or more frequency bands is20 MHz.
 18. The station of claim 12, wherein the non-legacy signal fieldis a high efficiency signal-A (HE-SIG-A) field.
 19. The station of claim12, wherein the duration is for setting a network allocation vector(NAV) by another station, wherein the another station is not adestination of the uplink frame.
 20. A computer-implemented method offacilitating multi-user communication in a wireless network, the methodcomprising: receiving a trigger frame; generating an uplink frame inresponse to the trigger frame, the uplink frame comprising a signal-A(SIG-A) field, wherein the SIG-A field comprises an indication whetherthe uplink frame uses an uplink multi-user (UL MU) frame format or anon-UL MU frame format, wherein the SIG-A field comprises informationassociated with a transmission opportunity (TXOP) duration, and whereinthe information is generated based on a duration indicated in thetrigger frame; and providing the uplink frame for transmission.